It's time for the United States and its European allies to raise or fold.

Russian President Vladimir Putin clearly called their bluff on Tuesday, announcing steps for his country to annex the Crimean Peninsula from neighboring Ukraine.

President Barack Obama and European allies had warned such a move would bring tougher sanctions and diplomatic isolation, but there was little immediate response Tuesday to Putin's bold pronouncement in the Russian parliament.

The White House announced that Obama invited leaders of the G7 industrial powers to meet next week on the sidelines of a nuclear security summit in the Netherlands to discuss the Ukraine crisis.

Presumably, such a gathering by Obama and his counterparts from Britain, France, Germany, Italy, Japan and Canada would consider scrapping their annual summit with Russia planned for July in Sochi, and perhaps kicking Putin out of the G8 club altogether.

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Both moves have been threatened, with the G7 nations already halting preparations for the Sochi meeting.

G8 summit in doubt?

White House spokesman Jay Carney strongly hinted Tuesday that it would get scrapped, telling reporters that "preparations for that summit have been suspended, summits don't occur without preparations" and "those preparations look unlikely to resume any time soon."

On Monday, Obama and the European Union imposed sanctions on specific Russian and Crimean officials as part of steps intended to be easily expanded if necessary.

Carney said the moves already hurt the Russian economy and the ruble currency, and he indicated further actions were coming.

"You have seen some designations already and there are more to come," he said of individuals cited for sanctions.

"I wouldn't, if I were you, invest in Russian equities right now unless you were going short," Carney advised, in reference to investors speculating on a losing venture.

However, Carney made clear that the U.S. approach focused for now on isolating Russia diplomatically and economically.

"This action -- the results of the referendum and the attempts to annex a region of Ukraine illegally -- will never be recognized by the United States" and the international community, he said, with "further actions, further provocations" by Russia leading to "higher costs."

Secretary of State John Kerry had a more reflective take, telling a town hall-style meeting that the administration still hoped for a diplomatic solution "but today was very confrontational and very triumphalist about something that is a breach of international law, and I think people are deeply concerned about it."

Biden: Crimea was a "land grab"

Meanwhile, Vice President Joe Biden began a tour of former Soviet bloc nations now NATO allies by pledging the full support of the strategic alliance against any Russian aggression similar to what has occurred in Ukraine.

"Our intent is that NATO emerge from this crisis stronger and more unified than ever," Biden said at his first stop in Warsaw. "Our commitment is absolutely unwavering and unshakeable."

He noted the United States deployed more jet fighters in the region to bolster NATO air policing, and he called Putin's moves to add Crimea to the Russian Federation a "blatant, blatant violation of international law" and "nothing more than a land grab."

Speaking to reporters at a joint news conference with Polish Prime Minister Donald Tusk, Biden said Russia responded to Ukraine's efforts to realize a more democratic future "with a brazen, brazen military incursion, with a purposeful ratcheting up of ethnic tensions inside Ukraine, with a rushed and illegal referendum in Crimea that was, not surprisingly, rejected by virtually the entire world."

Biden also warned Moscow that its political and economic isolation will increase if it continues such aggression, and he reiterated support for Ukraine in the form of a billion-dollar loan guarantee as well as technical assistance to prepare for elections and support for reforms that will allow the International Monetary Fund to provide a stabilization package to the cash-strapped country.

The vice president's visit comes two days before European Union leaders will meet in Brussels for talks certain to include the Ukraine crisis.

Putin unfazed so far

For his part, Putin appeared unfazed by the initial U.S. and EU steps, telling the parliament on Tuesday that Russia already races lingering sanctions from the Cold War that still exist in practice.

He called the events that led to last month's ouster of Ukrainian President Viktor Yanukovych a "state coup" carried out through "terror and murders and pogroms" by "Russiaphobes and anti-Semites."

The United States rejects Putin's characterization of the Ukraine political upheaval, instead calling it a demonstration of democratic aspirations by the Ukrainian people.

Underlying the conflict was Yanukovych's moves prior to his ouster to align more closely with Moscow instead of proceeding with a shift toward closer association with the EU.

At home, Obama has come under criticism from Republicans who complain an unwillingness by the administration to take on Putin on other issues has now emboldened the Russian leader.

Conservative Sen. John McCain of Arizona called for more sanctions against Russia and increased assistance for Ukraine, a stance backed by House Majority Leader Eric Cantor of Virginia.

"I support the President's decision to issue sanctions against Russian leaders, but that list must be dramatically expanded to exert real pressure," Cantor said Tuesday, also urging that Russia be kicked out of G8 and for the United States to provide military support needed by Ukraine.